It’s a problem whenever you will be writing data over an extended period of time. This will frequently be the case for RAID systems (atlhough WD claims it won’t be for small personal RAIDs - an assertion I question.)
But it also will be an issue for making backups. For instance, my initial Time Machine backup wrote 900GB to the new drive. It took about 3 hours to complete (an average of 83 MB/s for three hours). SMR would definitely slow this down.
On the other hand, after the initial backup, subsequent backups (which rarely writes more than 1GB, usually less) probably wouldn’t be affected much.
RAID is an especially nasty case, where the performance problems may result in the RAID software declaring the drive dead, removing it from the array, but a slow-performing drive in other circumstances can still be unacceptable even if it’s not a total catastrophe.
IMO, SMR is not appropriate for any situation that is expected to involve extended periods of write operations. Off the top of my head, this includes:
- A volume containing swap files/partitions
- An active transaction database (typically a server application)
- Video/audio capture and editing
- Backup devices (especially non-incremental backups where you may be writing hundreds of gigabytes in a single session)
I think there are plenty of applications where large writes happen infrequently (if at all), and SMR shouldn’t be a problem there. But in many cases, you don’t really know (at the time of purchase) what use-cases you will encounter over the life of the drive.
Furthermore, the difference in price isn’t very great. My most recent shopping run showed a difference of $15-25 for a 4TB drive (Seagate Barracuda vs. a Seagate IronWolf, Toshiba X300 or Toshiba N300). And those drives differ in more ways than just SMR-vs-CMR (e.g. the IronWolf and N300 are rated for 24x7 operation vs 8x5. The two Toshiba models are 7200 RPM vs 5400/5900 RPM for the two Seagate models).
In my particular case, since I was explicitly looking for a 7200 RPM drive rated for 24x7 operation, that ended up (coincidentally?) eliminating all of the SMR drives from consideration anyway, so the question ended up being moot for my specific situation.